The mechanical success of cable tool drilling has
greatly depended on a device called jars, invented by a
spring pole driller, William Morris, in the salt well
days of the 1830's. Little is known about Morris except
for his invention and that he listed Kanawha County (now
in West Virginia) as his address. Morris patented this
unique tool in 1841 for artesian well drilling. Later,
using jars, the cable tool system was able to
efficiently meet the demands of drilling wells for oil.

The jars were improved over time, especially at the
hands of the oil drillers, and reached the most useful
and workable design by the 1870's, due to another patent
in 1868 by Edward Guillod of Titusville, Pennsylvania,
which addressed the use of steel on the jars' surfaces
that were subject to the greatest wear. Many years
later, in the 1930's, very strong steel alloy jars were
made.

A set of jars consisted of two interlocking links
which could telescope. In 1880 they had a play of about
13 inches such that the upper link could be lifted 13
inches before the lower link was engaged. This
engagement occurred when the cross-heads came
together.Today, there are two primary types, hydraulic
and mechanical jars. While their respective designs are
quite different, their operation is similar. Energy is
stored in the drillstring and suddenly released by the
jar when it fires. Jars can be designed to strike up,
down, or both. In the case of jarring up above a stuck
bottomhole assembly, the driller slowly pulls up on the
drillstring but the BHA does not move. Since the top of
the drillstring is moving up, this means that the
drillstring itself is stretching and storing energy.
When the jars reach their firing point, they suddenly
allow one section of the jar to move axially relative to
a second, being pulled up rapidly in much the same way
that one end of a stretched spring moves when released.
After a few inches of movement, this moving section
slams into a steel shoulder, imparting an impact load.

In addition to the mechanical and hydraulic versions,
jars are classified as drilling jars or fishing jars.
The operation of the two types is similar, and both
deliver approximately the same impact blow, but the
drilling jar is built such that it can better withstand
the rotary and vibrational loading associated with
drilling. Jars are designed to be reset by simple string
manipulation and are capable of repeated operation or
firing before being recovered from the well. Jarring
effectiveness is determined by how rapidly you can
impact weight into the jars. When jarring without a
compounder or accelerator you rely only on pipe stretch
to lift the drill collars upwards after the jar releases
to create the upwards impact in the jar. This
accelerated upward movement will often be reduced by the
friction of the working string along the sides of the
well bore, reducing the speed of upwards movement of the
drill collars which impact into the jar. At shallow
depths jar impact is not achieved because of lack of
pipe stretch in the working string.

When pipe stretch alone cannot provide enough energy
to free a fish, compounders or accelerators are used.
Compounders or accelerators are energized when you over
pull on the working string and compress a compressible
fluid through a few feet of stroke distance and at the
same time activate the fishing jar. When the fishing jar
releases the stored energy in the compounder/acclerator
lifts the drill collars upwards at a high rate of speed
creating a high impact in the jar.

System Dynamics of Jars

Jars rely on the principle of stretching a pipe to
build elastic potential energy such that when the jar
trips it relies on the masses of the drill pipe and
collars to gain velocity and subsequently strike the
anvil section of jar. This impact results in a force, or
blow, which is converted into energy.

History of Power Swivel Developmentby
Larry Keast, P.E., Founder and CEO
Venturetech Corporation International

This brief history is
written from my experience since 1980, from researching Gulf
Publishing's Composite Catalogs, and from stories told to me. Until
Venturetech's XK power swivels, the only real player in this business
was Bowen, although there were others along the way. There have also
been a few non-engineering companies building poorly-designed equipment
and even direct Bowen copies, and there have been fabrication packagers
who buy a Bowen swivel and put it on their own power unit. In this
history, I have only included power swivels designed and built by
engineering-based manufacturing companies.

1948 - The first power
swivels appeared in the Composite Catalog. Baash-Ross and Homco each had
a full page, and the S.R. Bowen Company offered one introductory
sentence with no photo or other information. The largest of these first
power swivels were rated up to 2000 ft-lbs torque, 40 tons capacity, and
31 rpm. Engines were up to 12 HP, and gear and vane-type hydraulic pumps
and motors operated around 1000 psi.

1950 - S.R. Bowen Company
added a full catalog sheet on their very similar "powered swivel".

About 1960, Baash-Ross
was bought by Joy Manufacturing and in 1962 they introduced their 65 ton
and 100 ton power swivels. Then about 1980, Baash-Ross introduced
well-engineered upgrades of these models, calling them the PS-85 and
PS-130. They only made them until Varco bought Baash-Ross and
discontinued these swivels altogether in the early 90's. We continue
providing parts for these swivels.

Other than Bowen, Baash-Ross,
Homco, and King were the only power swivels under 250 tons designed and
built in engineering-based manufacturing companies. They never competed
effectively with Bowen after 1970, whose leadership was due to much more
aggressive sales and marketing than the others.

In 1964, Bowen introduced
the 85 ton S-2 and the 120 ton S-3. These models employed early Vickers
piston-type hydraulic motors which were limited to 3000 psi and had to
be bolted on from the inside of the gearbox before swivel assembly.

In the 1970's, after not
offering a swivel for years, Homco developed their own ingenious power
swivels, but they were too expensive and too large to be practical. They
never got off the ground, and after a few years, Homco started buying
Bowens for use in their service operations.

King Oil Tools has been
known since the 50's for their complete line of water well and workover
swivels, not power swivels. King introduced 90 and 130 ton power swivels
in the late 70's, and some have been sold through the years, but they
were never a major competitor.

In 1972, Bowen Introduced
the S-2.5 and in 1973, the S-3.5. The load ratings remained the same as
the previous S-2 and S-3, and the appearance was almost the same, but
the gearing and main body were redesigned for higher torques. To
increase torque, they used the new Sundstrand 5000 psi piston-type
closed loop hydraulics including variable displacement pumps. High
pressure piston equipment was new to the oilfield at the time, and gear
and vane-type pumps and motors were still limited to 2500 psi. It's
important to note that the oilfield didn't understand that the new high
pressure piston equipment was extremely dirt sensitive.

So the Bowen 2.5 and 3.5
have been around more than 30 years - so long that their model numbers
became generic, a fine thing for Bowen. As a result, people incorrectly
refer to other brands of power swivels by Bowen model numbers, and our
customers ask if we make a 2.5 or 3.5. We explain those are Bowen's
model numbers and our XK-90 and XK-150 swivels are quite different,
although they compete directly.

Typical of big companies
growing by merger and acquisition, when IRI bought Bowen in the 1990's,
some marketing guru or committee made the ill-informed decision to
change model numbers. That would have been a great idea in the
beginning, before the 2.5 and 3.5 became generic. The goal was to give
all their power swivels consistent model numbers reflecting the tonnage
rating. So the S-2.5 was renamed S-85 for 85 tons, and the S-3.5 renamed
S-120 for 120 tons. As part of this renaming exercise, they changed
their power units, using later model engines, pumps, some lower cost
components, and a poorly designed triple power hose reel destined for
long term problems. The swivel heads remained unchanged. The world still
refers to the 2.5 and 3.5, and we have even heard field people refer to
the 4.5, logically thinking it meant Bowen's 250 ton, which it never
did.

Then when National-Oilwell
bought IRI in 2000, they even deleted the Bowen name from their
advertising, a name which had earned a respected reputation around the
world. Mr. Bowen must have rolled over in his grave.

This has all been very
confusing, customers in the field don't understand, and no doubt most
National-Oilwell people don't know this history.

Our only business is
power swivels, and for many years, we have made replacement parts for
Bowen, Baash-Ross, and other brands no longer in production. Everyday,
we ship replacement parts worldwide. But as a creative design engineer
and inventor, I never wanted to copy the whole Bowen machines, because
that would be an insult to my creativity and to Mr. Bowen's hard work
building his company. I suppose I'm a bit unusual since the oilfield is
filled with companies copying the originator's products. It's all legal
after the patents run out, and they probably make more money than we do,
but I just wouldn't have any fun. I'm sure the original Bowen design
engineers would approve of our work, and it's not that their designs
were bad, just different; and they didn't have today's hydraulic
components to work with.

We have been successful
because power swivels are the only product line we have focused on for
25 years. All the other manufacturing companies were much larger and had
many product lines unrelated to power swivels which diluted their
attention.

Finally, I'm an old hot
rodder and motorhead, and I love cars, trucks, and engines. When I
discovered this power swivel business niche had diesel engines,
technical hydraulics, and remote pneumatic controls, it was very
interesting to me, looked like fun, and seemed like something I could do
with excellence. That has proven to be the case, and I'm grateful. I'm
also grateful to have a great team of people who love this equipment as
much as I do. We enjoy working together to build first class machinery
for our customers and we look forward to continued development.